Cemented carbide is used for manufacturing sintered bodies for e.g. cutting tools, wear parts, rock drill bits, etc. The cemented carbide industry is also interested in producing materials that are hard and have wear resistant to be used at high speed conditions. This is achieved by coating cemented carbides with layers of e.g. TiN, Ti(C, N), (Ti, Al)N and/or Al2O3.
In U.S. Pat. No. 4,277,283, the cemented carbides are sintered so that a gradient is formed, thus a surface zone is created which is cobalt enriched and free from gamma phase. This is usually performed by incorporating carbonitrides as raw materials.
WO 2012/145773 relates to a tungsten monocarbide powder formed of a hexagonal tungsten carbide doped with at least one group 4 and/or group 5 and/or group 7 transition metal (excluding Tc). The document also discloses a two-stage method for producing novel doped hexagonal tungsten carbides via (W, Me)2C to (W, Me)C.
Reichel, B et al (International Journal of Refractory Metals and Hard Materials 28 (2010) 638-645) discloses a method for the production of doped hard metals with individual carbides. According to the method, double or triple alloyed sub-carbides of the type MexCoyCz (wherein Me=metal such as W, V, Cr, Ta, Ti etc) are used as starting materials to produce hardmetals containing WC or WC/cubic carbide phase embedded in a Co binder phase. However, this method has problems with adjusting the carbon content to produce defect free structures (such as eta-phase or free-graphite) since extra carbon need to be added to the starting MexCoyCz subcarbides to produce the final desired microstructure. Furthermore, it has never been proved that by using the method described a sintered hardmetal containing hex WC doped with any cubic carbide can be produced.
When using hex-doped WC, the main challenge from a processing point of view, is to avoid the precipitation of the doping transition metal in the form of a carbide or carbonitride out of the hex-doped WC phase during the sintering process and none of the methods disclosed above solves this problem. Additionally, for certain applications of cemented carbides, there is also a challenge to avoid precipitation of cubic carbides as these will reduce the toughness of the obtained sintered product.
Thus, the process and the product obtained thereby disclosed in the present disclosure will migrate and/or provide a solution to the problems mentioned above.